Blending of elastomers with other elastomers as well as non-elastomers to achieve a particular result is well known. Nevertheless, there still exist many applications where new compositions are required to obtain better performance from an existing elastomer.
One recent discovery which provides improved mechanical properties is described in a published European Patent Application, No. 178,752. The invention disclosed therein involves the modification of various rubbers by the addition of low molecular weight liquid telechelic polymers to produce a highly extensible product which is as good as or better than the unmodified rubber in terms of abrasion resistance and hot mechanical properties.
The rubbers modified include natural rubber and a variety of the common synthetic rubbers. The telechelic polymers added contain various functionalities including carboxyl, amine, hydroxy, epoxy and modifications thereof. In order to blend the two together a linking agent is employed including reactive metal compounds, organo-metallic compounds and multi-functional epoxides.
The present invention does not rely on the addition of telechelic polymers, nor does it require a linking agent. The material blended with the elastomer is a block copolymer described in U.S. Pat. No. 3,838,108. This patent, owned by the Assignee of record, described block copolymers comprising anionically polymerized olefins and other monomers and crystalline blocks from a variety of monomers including nylon forming, urea forming, urethane forming, imide forming and the like.
Despite the fact that these block copolymers were described over 12 years ago, there has been no recognition until now that they could be blended with certain elastomers to provide improved mechanical properties.